If you're among those who want the 'dark theme' back on your Q10 or available for your Z10, you now have the option of making that happen thanks to some files from the Berry Leaks team. There is a few small caveats that you'll want to pay attention to though, like the fact you need to be on specific OS' and you'll need to sideload the files but overall, that's pretty minor stuff if you're really wanting the dark theme options for your contacts and calendar.
You'll want to hit up the CrackBerry Forums for the full details on which OS' and devices are supported and if you're not really feeling going through the sideloading process, remember this option of theme choice will be coming to a later BlackBerry 10 OS revision. Also keep in mind these files, while taken from a BlackBerry 10 OS, are not really official so you're loading these files at your own risk.
Bad things can happen, if you're not down with that then best to skip this.